Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$85.95	12.102%	$96.3517	$96.35	$96.35	$96.40
Purchase #2	$88.89	7.320%	$95.3967	$95.40	$95.40	$95.40
Purchase #3	$117.32	5.332%	$123.5755	$123.58	$123.60	$123.60
Purchase #4	$40.60	4.853%	$42.5703	$42.57	$42.55	$42.60
Purchase #5	$76.89	6.275%	$81.7148	$81.71	$81.70	$81.70
Purchase #6	$94.45	7.248%	$101.2957	$101.30	$101.30	$101.30
Purchase #7	$246.82	12.807%	$278.4302	$278.43	$278.45	$278.40
7 purchase totals =	$750.92		$819.3349	$819.34	$819.35	$819.40